1. Technical Field
The present invention relates to a relative angle sensing device.
2. Related Art
Recently, there has been suggested a device for sensing a relative rotation angle between two rotary shafts coaxially arranged.
For example, a device described in Japanese Patent Application Laid Open Publication No. 2007-292550 is applied to an electric power steering apparatus, and is a device for sensing torque between an input shaft and an output shaft. The input shaft and the output shaft are connected with each other through a torsion bar. A magnetic generator is provided on the input shaft. The magnetic generator has a configuration in which a circular magnetic part is arranged on a back yoke formed of a circular magnetic body. A magnetic yoke part formed of a first magnetic yoke and a second magnetic yoke is arranged on the output shaft. The other end parts of the first magnetic yokes are connected with each other by a first magnetic ring, and the other end parts of the second magnetic yokes are connected with each other by a second magnetic ring. A first magnetic concentration ring is arranged on a housing so as to face the first magnetic ring. A second magnetic concentration ring is arranged on the housing so as to face the second magnetic ring. A first magnetic concentration yoke is arranged on the first magnetic concentration ring, and a second magnetic concentration yoke is arranged on the second magnetic concentration ring. Two pairs of convex parts are arranged on the first magnetic concentration yoke and the second magnetic concentration yoke, respectively, so as to face each other. Space between each pair of the convex parts is a magnetic gap, and a magnetic sensor is arranged inside the magnetic gap.
As a method for forming the magnetic generator, there has been suggested a method in which adhesive material is applied onto the rear surface of the magnetic body before magnetization, the magnetic body before magnetization is adhered to the back yoke with the adhesive material, and the magnetic body is magnetized after the back yoke is inserted into the input shaft with pressure.
In a case of peeling of the adhesive material between the back yoke and the magnet part (magnetic body after magnetization) configuring the magnetic generator, it is feared that the magnet part does not rotate together with one rotary shaft (for example, an input shaft) out of the two rotary shafts, and the relative rotation angle between the two rotary shafts is not sensed.
The present invention is intended to suggest a device that is able to sense a relative rotation angle between two rotary shafts even in a case of peeling of the adhesive material.